Telephone plug cord



Dec. 10,1929. w. 1. MIDDLETON TELEPHONE PLUG CORD Filed July 25, 1928'lNVENTOR Wash/yin l l/Md/efon ATTO'RNEYS Patented Dec. 10, 1929 UNITEDSTATES PATENT OFFICE SIMPLEX WIRE AND CABLE COMPANY, TION OFMASSACHUSETTS TELEPHONE Application filed July 25,

T his invention relates to improvementsin multi-conductor cables used toconnect pairs of jack plugs in the conventional telephone switchboard.These cables are commonly designated telephone plug cords. Theconventional cable now used for this purpose consists of threeconducting elements each made up of a number of strands of tinsel on acotton core enclosed within a silk wind and a braided jacket, the threeconducting elements together with suitable fillers being enclosed withina common outer braided jacket. This conventional cable has two seriousdisadvantages; it is expensive and itis .of relaf tively short usefullife. Replacement of such cable is frequently necessary as often as tenor twelve-times a year on busy switchboards. In such service the savingin operating expense possible by reducing the number of such re- 2placements exceeds any saving possible in reducing the cost-of thecable; The improved telephone plug cord of the present inventionislessexpensive than the conventional type of cord and it has theimportant advantage of 25 having a useful life exceeding fourfold ormore the usual life of the conventional type of cord. 1

Cables embodying the invention are illustrated in the accompanyi gdrawings and 30 the invention will be described in detail in connectiontherewith. In the accompanying drawings Fig. 1 is a fragment of one formof cable embodying the invention with parts broken away and Fig. 2 is asection of the cable shown in Fig. 1, and

Fig. 3 is. fragment of. another form of cable embodying the inventionwith parts broken away and Fig. 4 is a section of the cable shown inFig. 3.

Referring to Figs. 1 and 2, the cable comprises three conductingelements 5, 6 and 7 three filler elements 8, 9 and 10, a binder 11 andajacket 12. Each of the conducting elements 5, 6 and 7 comprises anon-conducting core 13 of soft fibrous material, a,plurality ofconducting wires 14, small in diameter with respect to the core 13,wound about the core in a short spiral, 8 to 10 turns per inch forexample, a non-conducting winding 15 OF BOSTON, MASSACHUSETTS, ACORPORA- PLUG CORD 1928. Serial No. 295,331.

elastic vulcanized rubber compounded to afford a maximum of physicalstrength and re-. sistance to abrasion. I Compounds of the type used asautomobile tire tread stocks are useful in this connection. 'A suitablerubber compound, for example, may consist of the following:

Parts Rubber -(smoked-sheets) 63 Zincoxide -Q 9 Carbon black a 24Ozokerite 2 Ethylidene-aniline -1 Di-phenyl-guanidine 'Sulphur 3 Thiscompound may be vulcanized at 270 F. for 30 minutes. The rubber jacket12 .'for example, may be of 0.022"0.'034"- in thickness.

Thesecables arefinished to an outer diameter Referring to Figs. 3 and 4,the cable is of construction identical with that illustrated in Figs. 1and 2 except in that a braided jacket 17 is inter osed between the outerrubber jacket and t e bound group. of conducting elements and fillerelements. This interposed jacket.17 may be a 40/2 soft cotton braid, forexample. This interposed braidedjacket further improves the flexibilityof the complete cable. I

In each of the cables just described in detail the conducting elementsand the filler ele-' ments, the latter being small with respect to theformer, are s'piralled together and bound to form a strong yet flexiblecomposite. The conducting elements and filler elements are boundtogether independently of the encasing rubber acket. Within thiscomposite the construction of the individual conducting elementsprovides the requisite flexibility. The conducting wires are wound onthe core 5 in a short spiral and, with-advantage, are

arranged in a spiralled group with successive turns of the group spacedfrom the preceding turns. This particular construction makes possiblethe use of wire as the conducting element instead of the usual tinsel.This composite, then, encased within the outer elastic vulcanized rubberjacket is protected against mechanical disturbance and, with the addedstrength of a rubber jacket of the 5 type specified, provides a completecable of unusual lifeyet having all of the other properties requisite tothis class of service and at the same time relatively inexpensive. Iclaim: 1. An improved telephone plug cord, consisting of a pluralit ofconducting elements and a plurality of Her elements small'with respectto the conducting elements spiralled together and encased in an outerjacket of r 5 elastic vulcanized rubber, said spiralled conduct-ingelements and filler elements being boundtogether independently of theencasing jacket, said conducting elements each consisting of anon-conducting core, a plurality of conducting wires small with respectto the core wound thereon in a short spiral, a winding of non-conductingmaterial thereover and an encasing braided acket.

2. An improved telephone plug cord, con- 5 sisting of a plurality ofconducting elements and a plurality of filler elements small withrespect to the conducting elements spiralled together and encased in anouter'jacketof elastic vulcanized rubber, said spiralled con- 40 iducting elements and filler elements being bound together independentlyof'the encasing jacket, said conducting elementsv each consisting of anon-conducting core, a plurality of conducting wires sma l with re ect;to the core wound thereon in a short spiral,

a winding of non-conducting material thereover and an encasing braidedjacket, said plurality of conducting wires arranged in a group withsuccessive turns of the group spaced from preceding turns.

In testimony whereof I afiix my signature WASHINGTON IRVING MIDDLETON;

